Astronomy Cmarchesin: October 2020

Saturday, October 31, 2020

Hubble Finds ‘Greater Pumpkin’ Galaxy Pair

This is a Hubble Space Telescope snapshot of the early stages of a collision between two galaxies that resembles a Halloween carved pumpkin. The "pumpkin's" glowing “eyes” are the bright, star-filled cores of each galaxy that contain supermassive black holes. An arm of newly forming stars give the imaginary pumpkin a wry smirk. The two galaxies, cataloged as NGC 2292 and NGC 2293, are located about 120 million light-years away in the constellation Canis Major. Credits: NASA, ESA, and W. Keel (University of Alabama). Hi-res image

Sorry Charlie Brown, NASA's Hubble Space Telescope is taking a peek at what might best be described as the "Greater Pumpkin," that looks like a Halloween decoration tucked away in a patch of sky cluttered with stars. What looks like two glowing eyes and a crooked carved smile is a snapshot of the early stages of a collision between two galaxies. The entire view is nearly 109,000 light-years across, approximately the diameter of our Milky Way.

The overall pumpkin-ish color corresponds to the glow of aging red stars in two galaxies, cataloged as NGC 2292 and NGC 2293, which only have a hint of spiral structure. Yet the smile is bluish due to newborn star clusters, spread out like pearls on a necklace, along a newly forming dusty arm. The glowing eyes are concentrations of stars around a pair of supermassive black holes. The scattering of blue foreground stars makes the "pumpkin" look like it got all glittery for a Halloween party.

What's going on in this pumpkin-like pair?

If you mix two fried eggs together, you get something resembling scrambled eggs. The same goes for galaxy collisions throughout the universe. They lose their flattened spiral disk and the stars are scrambled into a football-shaped volume of space, forming an elliptical galaxy. But this interacting pair is a very rare example of what may turn out to result in a bigger fried egg—the construction of a giant spiral galaxy. It may depend on the specific trajectory the colliding galaxy pair is following. The encounter scenario must be rare because there's only a handful of other examples in the universe, say astronomers.

The ghostly arm making the "smile" may be just the beginning of the process of rebuilding a spiral galaxy, say researchers. The arm embraces both galaxies. It most likely formed when interstellar gas was compressed as the two galaxies began to merge. The higher density precipitates new star formation.

The dynamic duo hides out 120 million light-years away in the constellation Canis Major, so it is seen far behind the star-filled foreground plane of our Milky Way galaxy. Therefore, it's a difficult area to pinpoint far-flung distant background galaxies from the plethora of stars seen in the field.

Halloween is scarier with Hubble! What looks like two glowing eyes and a crooked carved smile is a snapshot of the early stages of a collision between two galaxies. This new image is just one of several spooky views Hubble has captured in the universe.Credits: NASA's Goddard Space Flight Center. Download this video in HD formats from NASA Goddard’s Scientific Visualization Studio

The galaxy pair was similar to objects tagged by the citizen-science project Galaxy Zoo, where volunteers go hunting for oddball-looking galaxies. Astronomer William Keel, of the University of Alabama in Tuscaloosa, included several of these in the "Gems of the Galaxy Zoos" Hubble program, which is observing several kinds of rare galaxies during short gaps between other scheduled Hubble observations. The Hubble image brought out new details of the close encounter.

Keel speculates that the ultimate destiny for this pair will be to merge into a giant luminous spiral galaxy like UGC 2885, Rubin's Galaxy, which is over twice the diameter of our Milky Way. Hubble has caught a snapshot of the groundbreaking early stages of a galactic makeover.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy in Washington, D.C.

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

Science Contact:

William Keel
University of Alabama, Tuscaloosa, Alabama
keel@ua.edu

Source: NASA/Solar System and Beyond

Stars and Skulls: new ESO image reveals eerie nebula

PR Image eso2019a

New ESO’s VLT image of the Skull Nebula

PR Image eso2019b

The Skull Nebula in the constellation of Cetus (The Whale)

PR Image eso2019c

The sky around the Skull Nebula

Videos

Friday, October 30, 2020

A Quick Look: Assessing The Habitability of Planets Around Old Red Dwarfs

Assessing The Habitability of Planets Around Old Red Dwarfs

GJ 699 (Barnard's Star)

Credit: X-ray light curve: NASA/CXC/University of Colorado/K. France et al.;

Illustration: NASA/CXC/ M. Weiss)

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Tour: Einstein's Theory of Relativity, Critical for GPS, Seen in Distant Stars - More Animations

A new study using data from NASA's Chandra X-ray Observatory and Hubble Space Telescope gives new insight into an important question: how habitable are planets that orbit the most common type of stars in the Galaxy? The target of the new study, as reported in our press release, is Barnard's Star, which is one of the closest stars to Earth at a distance of just 6 light years. Barnard's Star is a red dwarf, a small star that slowly burns through its fuel supply and can last much longer than medium-sized stars like our Sun. It is about 10 billion years old, making it twice the age of the Sun.

The authors used Barnard's Star as a case study to learn how flares from an old red dwarf might affect any planets orbiting it. This artist's illustration depicts an old red dwarf like Barnard's Star (right) and an orbiting, rocky planet (left).

The research team's Chandra observations of Barnard's Star taken in June 2019 uncovered one X-ray flare (shown in the inset box) and their Hubble observations taken in March 2019 revealed two ultraviolet high-energy flares (shown in an additional graphic). Both observations were about seven hours long and both plots show X-ray or ultraviolet brightness extending down to zero. Based on the length of the flares and of the observations, the authors concluded that Barnard's Star unleashes potentially destructive flares about 25% of the time.

Credit: X-ray light curve: NASA/CXC/University of Colorado/K. France et al.; UV light curve: NASA/STScI;

The team then studied what these results mean for rocky planets orbiting in the habitable zone — where liquid water could exist on their surface — around an old red dwarf like Barnard's Star. Any atmosphere formed early in the life of a habitable-zone planet was likely to have been eroded away by high-energy radiation from the star during its volatile youth. Later on, however, planet atmospheres might regenerate as the star becomes less active with age. This regeneration process may occur by gases released by impacts of solid material or gases being released by volcanic processes.

However, the onslaught of powerful flares like those reported here, repeatedly occurring over hundreds of millions of years, may erode any regenerated atmospheres on rocky planets in the habitable zone. The illustration shows the atmosphere of the rocky planet being swept away to the left by energetic radiation from flares produced by the red dwarf. This would reduce the chance of these worlds supporting life. The team is currently studying high-energy radiation from many more red dwarfs to determine whether Barnard's Star is typical.

A paper describing these results, led by Kevin France of the University of Colorado at Boulder, appears in the October 30, 2020 issue of The Astronomical Journal and is available online. NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science and flight operations from Cambridge and Burlington, Massachusetts.

Fast Facts for GJ 699 (Barnard's Star):

Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 17h 57m 48.5s | Dec +04° 41´ 36.1"
Constellation: Ophiuchus
Observation Date: June 17, 2019
Observation Time: 7 hours 25 minutes
Obs. ID: 20619
Instrument: ACIS
References: France, K, et al., 2020, AJ, 160, 237; arXiv:2009.01259
Distance Estimate: About 5.97 light years

Source: NASA’s Chandra X-ray Observatory

About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets

This illustration depicts Kepler-186f, the first validated Earth-size planet to orbit a distant star in the habitable zone.

Credit: NASA Ames/JPL-Caltech/T. Pyle. Hi-res image

Since astronomers confirmed the presence of planets beyond our solar system, called exoplanets, humanity has wondered how many could harbor life. Now, we’re one step closer to finding an answer. According to new research using data from NASA’s retired planet-hunting mission, the Kepler space telescope, about half the stars similar in temperature to our Sun could have a rocky planet capable of supporting liquid water on its surface.

Our galaxy holds an estimated 300 million of these potentially habitable worlds, based on results in a study released today and to be published in The Astronomical Journal. Some of these exoplanets could even be our interstellar neighbors, with four potentially within 30 light-years of our Sun and the closest likely to be about 20 light-years from us.

This research helps us understand the potential for these planets to have the elements to support life. This is an essential part of astrobiology, the study of life’s origins and future in our universe.

The study is authored by NASA scientists who worked on the Kepler mission alongside collaborators from around the world. NASA retired the space telescope in 2018 after it ran out of fuel. Nine years of the telescope’s observations revealed that there are billions of planets in our galaxy – more planets than stars.

"Kepler already told us there were billions of planets, but now we know a good chunk of those planets might be rocky and habitable," said the lead author Steve Bryson, a researcher at NASA's Ames Research Center in California's Silicon Valley. "Though this result is far from a final value, and water on a planet's surface is only one of many factors to support life, it's extremely exciting that we calculated these worlds are this common with such high confidence and precision."

For the purposes of calculating this occurrence rate, the team looked at exoplanets between a radius of 0.5 and 1.5 times that of Earth's, narrowing in on planets that are most likely rocky. They also focused on stars similar to our Sun in age and temperature, plus or minus up to 1,500 degrees Fahrenheit.

That's a wide range of different stars, each with its own particular properties impacting whether the rocky planets in its orbit are capable of supporting liquid water. These complexities are partly why it is so difficult to calculate how many potentially habitable planets are out there, especially when even our most powerful telescopes can just barely detect these small planets. That's why the research team took a new approach.

This illustration depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of a star similar to our Sun. Credits: NASA Ames/JPL-Caltech/T. Pyle.

Rethinking How to Identify Habitability

This new finding is a significant step forward in Kepler's original mission to understand how many potentially habitable worlds exist in our galaxy. Previous estimates of the frequency, also known as the occurrence rate, of such planets ignored the relationship between the star's temperature and the kinds of light given off by the star and absorbed by the planet.

The new analysis accounts for these relationships, and provides a more complete understanding of whether or not a given planet might be capable of supporting liquid water, and potentially life. That approach is made possible by combining Kepler's final dataset of planetary signals with data about each star's energy output from an extensive trove of data from the European Space Agency's Gaia mission.

"We always knew defining habitability simply in terms of a planet's physical distance from a star, so that it's not too hot or cold, left us making a lot of assumptions," said Ravi Kopparapu, an author on the paper and a scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Gaia's data on stars allowed us to look at these planets and their stars in an entirely new way."

Gaia provided information about the amount of energy that falls on a planet from its host star based on a star's flux, or the total amount of energy that is emitted in a certain area over a certain time. This allowed the researchers to approach their analysis in a way that acknowledged the diversity of the stars and solar systems in our galaxy.

"Not every star is alike," said Kopparapu. "And neither is every planet."

Though the exact effect is still being researched, a planet's atmosphere figures into how much light is needed to allow liquid water on a planet's surface as well. Using a conservative estimate of the atmosphere's effect, the researchers estimated an occurrence rate of about 50% — that is, about half of Sun-like stars have rocky planets capable of hosting liquid water on their surfaces. An alternative optimistic definition of the habitable zone estimates about 75%.

An illustration representing the legacy of NASA's Kepler space telescope. After nine years in deep space collecting data that revealed our night sky to be filled with billions of hidden planets – more planets even than stars – NASA’s Kepler space telescope ran out of fuel needed for further science operations in 2018. Credits: NASA/Ames Research Center/W. Stenzel/D. Rutter. Hi-res image

Kepler's Legacy Charts Future Research

This result builds upon a long legacy of work of analyzing Kepler data to obtain an occurrence rate and sets the stage for future exoplanet observations informed by how common we now expect these rocky, potentially habitable worlds to be. Future research will continue to refine the rate, informing the likelihood of finding these kinds of planets and feeding into plans for the next stages of exoplanet research, including future telescopes.

"Knowing how common different kinds of planets are is extremely valuable for the design of upcoming exoplanet-finding missions," said co-author Michelle Kunimoto, who worked on this paper after finishing her doctorate on exoplanet occurrence rates at the University of British Columbia, and recently joined the Transiting Exoplanet Survey Satellite, or TESS, team at the Massachusetts Institute of Technology in Cambridge, Massachusetts. "Surveys aimed at small, potentially habitable planets around Sun-like stars will depend on results like these to maximize their chance of success."

After revealing more than 2,800 confirmed planets outside our solar system, the data collected by the Kepler space telescope continues to yield important new discoveries about our place in the universe. Though Kepler's field of view covered only 0.25% of the sky, the area that would be covered by your hand if you held it up at arm's length towards the sky, its data has allowed scientists to extrapolate what the mission's data means for the rest of the galaxy. That work continues with TESS, NASA's current planet hunting telescope.

"To me, this result is an example of how much we've been able to discover just with that small glimpse beyond our solar system," said Bryson. "What we see is that our galaxy is a fascinating one, with fascinating worlds, and some that may not be too different from our own."

For news media:

Members of the news media interested in covering this topic should reach out to the NASA Ames newsroom.

Author: Frank Tavares, NASA's Ames Research Center

Editor: Frank Tavares

Source: NASA/NASA Ames

Thursday, October 29, 2020

NASA’s Webb To Examine Objects in the Graveyard of the Solar System

Pluto and its largest moon, Charon, are two of the best-known residents of the Kuiper Belt. This composite of enhanced color images of Pluto (lower right) and Charon (upper left), was taken by NASA's New Horizons spacecraft as it passed through the Pluto system on July 14, 2015. The color and brightness of both Pluto and Charon have been processed identically to allow direct comparison of their surfaces, and to highlight the similarity between Charon's polar red terrain and Pluto's equatorial red terrain. Pluto and Charon are shown with approximately correct relative sizes, but their true separation is not to scale. Credits: NASA/JHUAPL/SwRI. Link to image

Beyond the orbit of Neptune, a diverse collection of thousands of dwarf planets and other relatively small objects dwells in a region called the Kuiper Belt. These often-pristine leftovers from our solar system's days of planet formation are called Kuiper Belt Objects, or Trans-Neptunian Objects. NASA's upcoming James Webb Space Telescope will examine an assortment of these icy bodies in a series of programs called Guaranteed Time Observations shortly after its launch in 2021. The goal is to learn more about how our solar system formed.

"These are objects that are in the graveyard of solar system formation," explained Cornell University's Jonathan Lunine, a Webb Interdisciplinary Scientist who will use Webb to study some of these targets. "They're in a place where they could last for billions of years, and there aren't many places like that in our solar system. We'd love to know what they're like."

By studying these bodies, Lunine and his colleagues hope to learn about which ices were present in the early solar system. These are the coldest worlds to display geologic and atmospheric activity, so scientists are also interested in comparing them with the planets.

Kuiper Belt Objects are very cold and faint, yet they glow in infrared light, which is at wavelengths beyond what our human eyes can see. Webb is specifically designed to detect infrared light. To study these distant objects, scientists mainly will use a technique called spectroscopy, which divides light into its individual colors to determine the properties of materials that interact with that light.

This global color mosaic of Neptune's moon Triton, likely a captured KBO, was taken in 1989 by Voyager 2 during its flyby of the Neptune system. Triton is by far the largest satellite of Neptune. Credit: NASA/JPL/USGS. Link to image

A Wide Assortment

The denizens of the Kuiper Belt come in various shapes and sizes. Some reside in pairs or multiples, while others have rings or moons. They exhibit a wide range of colors, which may indicate different formation histories or different exposure to sunlight.

"Some seem to be redder in color, others are bluer. Why is that?" said Heidi Hammel, a Webb Interdisciplinary Scientist for solar system observations. She is also Vice President for Science at the Association of Universities for Research in Astronomy (AURA) in Washington, D.C. "Using Webb, we will be able to get information about surface chemistry that might be able to give us some clues into why there are these different populations in the Kuiper Belt."

Kicked out of the Club

Between Jupiter and Neptune, and crossing the orbit of one or more of the giant planets, lies a different population of objects called centaurs. These are small solar system bodies that have been ejected from the Kuiper Belt. In addition to observing current Kuiper Belt Objects, these Webb programs will study such solar system bodies that have been "kicked out of the club." These former Kuiper Belt Objects have orbits that have been dramatically disturbed, bringing them significantly closer to the Sun.

"Because they cross the orbits of Neptune, Uranus, and Saturn, centaurs are short-lived. So they are typically only around for about 10 million years," explained John Stansberry of the Space Telescope Science Institute in Baltimore, Maryland. Stansberry is leading a different team that will use Webb to study Kuiper Belt Objects. "By that point, they have an interaction with one of the major planets that's very strong, and they either get thrown into the Sun or thrown out of the solar system."

Another body that Webb will study is Neptune's moon Triton. The largest of the ice giant's 13 moons, Triton shares many similarities with Pluto. "Even though it's Neptune's moon, we have evidence to suggest that it is a Kuiper Belt Object that got too close to Neptune sometime in its past, and it was captured into orbit around Neptune," said Hammel. "Triton was studied by the Voyager 2 probe in 1989. That spacecraft data will provide us very important 'ground truth' for our Webb observations of Kuiper Belt Objects."

Though not on Webb's target list, Arrokoth is probably exemplary of a lot of objects in the Kuiper Belt. The farthest object ever visited by a spacecraft, it is composed of two conjoined planetesimals. Arrokoth was photographed by the New Horizons spacecraft in December 2018 and January 2019. Credits: NASA/JHUAPL/SwRI/Roman Tkachenko. Link to image

A Sampling of the Targets

Here is a small sampling of some of the dozens of current and former Kuiper Belt Objects that Webb will observe:

Pluto and Charon: The dwarf planet Pluto and its largest moon, Charon, are two of the most well-known residents of the Kuiper Belt. Pluto boasts an atmosphere, haze, and seasons. It has geologic activity on its surface and may have an ocean in its interior. In addition to Charon, it hosts four other moons: Nix, Hydra, Styx, and Kerberos. The Webb data will complement the observations made by NASA's New Horizons spacecraft when it flew by the Pluto system in 2015.

Eris: Nearly the size of Pluto, Eris is the second-largest known dwarf planet in the solar system. At its farthest point, mysterious Eris is more than 97 times as far from the Sun as the Earth is. Because of its distance, it is difficult to observe, but Webb will tell scientists quite a bit about what kinds of ices are on its surface.

Sedna: With its deep red hue, Sedna is actually located beyond the main Kuiper Belt. It takes approximately 11,400 years to complete one orbit, and the farthest point of that highly elongated orbit is estimated to be 940 times Earth's distance from the Sun.

Haumea: This large, rapidly spinning body is egg-shaped, and scientists would like to know why. In addition to moons, it also seems to have a ring system. With Webb, scientists hope to learn more about how those rings formed.

Chariklo: The largest centaur, Chariklo is also the first asteroid found to have a ring system. It was the fifth ring system found in our solar system—after Saturn, Jupiter, Uranus and Neptune. The rings are believed to be between two and four miles wide.

Another program, called a Target of Opportunity, will observe a Kuiper Belt Object passing in front of a star, if such an alignment should occur during the first two years of Webb's lifetime. Called an occultation, this type of observation can reveal an object's size.

The few spacecraft that have flown by Kuiper Belt Objects could only study these intriguing objects for a very short period of time. With Webb, astronomers can target more Kuiper Belt Objects over an extended time. The result will be new insights into our solar system's earliest history.

The James Webb Space Telescope will be the world's premier space science observatory when it launches in 2021. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency.

For more information about Webb, visit www.nasa.gov/webb.

By Ann Jenkins
Space Telescope Science Institute, Baltimore, Md.

Editor: Lynn Jenner

Source: NASA/Webb Telescope

Wednesday, October 28, 2020

Galaxies in the Infant Universe Were Surprisingly Mature

Artist's illustration of a dusty, rotating distant galaxy

Artist's illustration of a galaxy in the early universe that is very dusty and shows the first signs of a rotationally supported disk. In this image, the red color represents gas, and blue/brown represents dust as seen in radio waves with ALMA. Many other galaxies are visible in the background, based on optical data from VLT and Subaru. Credit: B. Saxton NRAO/AUI/NSF, ESO, NASA/STScI; NAOJ/Subaru. Hi-Res File

Artist's animation of a dusty, rotating distant galaxy

Artist's animation of a galaxy in the early universe that is very dusty and shows the first signs of a rotationally supported disk. In this image, the red color represents gas, and blue/brown represents dust as seen in radio waves with ALMA. Many other galaxies are visible in the background, based on optical data from VLT and Subaru. Credit: B. Saxton NRAO/AUI/NSF, ESO, NASA/STScI; NAOJ/Subaru. Download Video

ALMA image of two dusty galaxies

These are two of the galaxies in the early universe that ALMA observed in radio waves. The galaxies are considered more "mature" than "primordial" because they contain large amounts of dust (yellow). ALMA also revealed the gas (red), which is used to measure the obscured star-formation and motions in the galaxies. Credit: B. Saxton NRAO/AUI/NSF, ALMA (ESO/NAOJ/NRAO), ALPINE team. Hi-Res File

Press Release Video
Brief video explaining this research result.
Credit: B. Saxton NRAO/AUI/NSF

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ALMA telescope conducts largest survey yet of distant galaxiers in the early universe

Massive galaxies were already much more mature in the early universe than previously expected. This was shown by an international team of astronomers who studied 118 distant galaxies with the Atacama Large Millimeter/submillimeter Array (ALMA).

Most galaxies formed when the universe was still very young. Our own galaxy, for example, likely started forming 13.6 billion years ago, in our 13.8 billion-year-old universe. When the universe was only ten percent of its current age (1-1.5 billion years after the Big Bang), most of the galaxies experienced a “growth spurt”. During this time, they built up most of their stellar mass and other properties, such as dust, heavy element content, and spiral-disk shapes, that we see in today’s galaxies. Therefore, if we want to learn how galaxies like our Milky Way formed, it is important to study this epoch.

In a survey called ALPINE (the ALMA Large Program to Investigate C+ at Early Times), an international team of astronomers studied 118 galaxies experiencing such a “growth spurt” in the early universe. “To our surprise, many of them were much more mature than we had expected,” said Andreas Faisst of the Infrared Processing and Analysis Center (IPAC) at the California Institute of Technology (Caltech).

Galaxies are considered more “mature” than “primordial” when they contain a significant amount of dust and heavy elements. “We didn’t expect to see so much dust and heavy elements in these distant galaxies,” said Faisst. Dust and heavy elements (defined by astronomers as all elements heavier than hydrogen and helium) are considered to be a by-product of dying stars. But galaxies in the early universe have not had much time to build stars yet, so astronomers don’t expect to see much dust or heavy elements there either.

“From previous studies, we understood that such young galaxies are dust-poor,” said Daniel Schaerer of the University of Geneva in Switzerland. “However, we find around 20 percent of the galaxies that assembled during this early epoch are already very dusty and a significant fraction of the ultraviolet light from newborn stars is already hidden by this dust,” he added.

Many of the galaxies were also considered to be relatively grown-up because they showed a diversity in their structures, including the first signs of rotationally supported disks – which may later lead to galaxies with a spiral structure as is observed in galaxies such as our Milky Way. Astronomers generally expect that galaxies in the early universe look like train wrecks because they often collide. “We see many galaxies that are colliding, but we also see a number of them rotating in an orderly fashion with no signs of collisions,” said John Silverman of the Kavli Institute for the Physics and Mathematics of the Universe in Japan.

ALMA has spotted very distant galaxies before, such as MAMBO-9 (a very dusty galaxy) and the Wolfe Disk (a galaxy with a rotating disk). But it was hard to say whether these discoveries were unique, or whether there were more galaxies like them out there. ALPINE is the first survey that enabled astronomers to study a significant number of galaxies in the early universe, and it shows that they might evolve faster than expected. But the scientists don’t yet understand how these galaxies grew up so fast, and why some of them already have rotating disks.

Observations from ALMA were crucial for this research because the radio telescope can see the star formation that is hidden by dust and trace the motion of gas emitted from star-forming regions. Surveys of galaxies in the early universe commonly use optical and infrared telescopes. These allow the measurement of the unobscured star formation and stellar masses. However, these telescopes have difficulties measuring dust obscured regions, where stars form, or the motions of gas in these galaxies. And sometimes they don’t see a galaxy at all. “With ALMA we discovered a few distant galaxies for the first time. We call these Hubble-dark as they could not be detected even with the Hubble telescope,” said Lin Yan of Caltech.

To learn more about distant galaxies, the astronomers want to point ALMA at individual galaxies for a longer time. “We want to see exactly where the dust is and how the gas moves around. We also want to compare the dusty galaxies to others at the same distance and figure out if there might be something special about their environments,” added Paolo Cassata of the University of Padua in Italy, formerly at the Universidad de Valparaíso in Chile.

ALPINE is the first and largest multi-wavelength survey of galaxies in the early universe. For a large sample of galaxies the team collected measurements in the optical (including Subaru, VISTA, Hubble, Keck and VLT), infrared (Spitzer), and radio (ALMA). Multi-wavelength studies are needed to get the full picture of how galaxies are built up. “Such a large and complex survey is only possible thanks to the collaboration between multiple institutes across the globe,” said Matthieu Béthermin of the Laboratoire d’Astrophysique de Marseille in France.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

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Media contact:

Iris Nijman
NRAO News and Public Information Manager
inijman@nrao.edu

A list of ALPINE publications to date can be found here (including eight papers appearing in Astronomy & Astrophysics today): http://alpine.ipac.caltech.edu/#publications

All ALPINE papers are dedicated to the memory of Olivier Le Fèvre, Principal Investigator of ALPINE.

Co-Principal Investigators of ALPINE are:
– Andreas Faisst, Caltech/IPAC, USA
– Lin Yan, Caltech, USA
– Peter Capak, Caltech/IPAC, USA
– John Silverman, Kavli Institute for the Physics and Mathematics of the Universe, Japan
– Matthieu Béthermin, Laboratoire d’Astrophysique de Marseille, France
– Paolo Cassata, University of Padua, Italy
– Daniel Schaerer, University of Geneva, Switzerland

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

Source: National Radio Astronomy Observatory (NRAO)/News

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Tuesday, October 27, 2020

Data reveals evidence of molecular absorption in the atmosphere of a hot Neptune

LTT9779b

Source: http://news.unm.edu/news/data-reveals-evidence-of-molecular-absorption-in-the-atmosphere-of-a-hot-neptune

An international team of scientists recently measured the spectrum of the atmosphere of a rare hot Neptune exoplanet, whose discovery by NASA's Transiting Exoplanet Survey Satellite (TESS) was announced just last month.

The discovery was made with data provided from the now-retired NASA Spitzer Space Telescope, which allows a unique, infrared view of the universe to look into regions of space that are hidden from optical telescopes.

One of the main goals of NASA’s TESS mission is to find new, small planets that would be good targets for atmospheric characterization. Early in its mission, it found LTT9779b, a planet orbiting a Sun-like star located 260 light years away from Earth. This planet, a little larger than Neptune, orbits very close to its star. The planet is found in the "hot Neptune desert," where planets shouldn't exist. Indeed, most close-in hot exoplanets are either gas giants the size of Jupiter or Saturn that have enough mass to retain most of their atmosphere using their high gravity against the evaporation caused by the star, or small rocky exoplanets that have lost their atmosphere to the star long ago.

“This ultra-hot Neptune is a ‘medium-sized’ exoplanet that orbits very close to its star (it takes just 19 hours to complete an orbit), but its low density indicates that it still has an atmosphere weighing at least 10 percent of the planet’s mass,” explained University of New Mexico Physics and Astronomy Assistant Professor Diana Dragomir, who is leading the work which involved more than 25 institutions.

The age of this system is 2 billion years. At this high temperature, the planet’s atmosphere should have evaporated long ago, early in the system’s life. “Hot Neptunes are rare, and one in such an extreme environment as this one is difficult to explain because its mass isn’t large enough to hold on to an atmosphere for very long. So how did it manage? LTT9779b had us scratching our heads, but the fact that it has an atmosphere gives us a rare way to investigate this type of planet, so we decided to probe it with another telescope,” Dragomir added.

To investigate its atmospheric composition and shed further light on its origin, scientists obtained secondary eclipse observations with the Spitzer Infrared Array Camera (IRAC) of the hot Neptune. The Spitzer observations confirmed an atmospheric presence and enabled a measurement of the planet's very high temperature, approximately 2,000 Kelvin (about 3,000 degrees Fahrenheit). “For the first time, we measured light coming from a planet that shouldn’t exist!” Said Dragomir.

After combining the Spitzer observations with a measurement of the secondary eclipse in the TESS bandpass, the scientists studied the resulting emission spectrum and identified evidence of molecular absorption in the planet’s atmosphere, which they believe is likely due to carbon monoxide. This molecule is not unexpected in the atmospheres of hot large planets (hot Jupiters), but to find it in a hot Neptune may provide clues on the origin of this planet and how it managed to hold onto its atmosphere. This result constitutes the first detection of atmospheric features in an exoplanet discovered by TESS, and the first-ever for an ultra-hot Neptune.

“If there’s a lot of atmosphere surrounding the planet, as is the case for \, then you can study it more easily,” said Dragomir. “A smaller atmosphere would be much harder to observe.” The results indicate that LTT9779b is an excellent target for additional characterization with NASA’s upcoming James Webb Space Telescope (JWST), which could also verify whether the observed molecular absorption is indeed due to carbon monoxide.

A companion paper, led by Kansas University Assistant Professor Ian Crossfield, also found signs that point to the planet’s atmosphere having a higher level of heavy elements than expected. This is additionally intriguing because the two similarly-sized planets in our Solar System, Neptune and Uranus, are primarily composed of light elements like hydrogen and helium.

“LTT9779 is one of those super-exciting targets, a very rare gemstone for our understanding of hot Neptunes. We believe we detected carbon-monoxide in its atmosphere and that the permanent dayside is very hot, while very little heat is transported to the night side,” said Björn Benneke, professor at Université de Montréal and member of the Institute for Research on exoplanets (iREx). “Both findings make LTT9779b say that there is a very strong signal to be observed making the planet a very intriguing target for future detailed characterization with JWST.”

Together, these results set the stage for similar investigations of a larger sample of exoplanets discovered in this hot Neptune desert, which are key to uncovering the origin of this unique population of exoplanets.

The research, Spitzer Reveals Evidence of Molecular Absorption in the Atmosphere of the Hot Neptune LTT 9779b, was published in The Astrophysical Journal Letters and supported in part by NASA through a Caltech/Jet Propulsion Laboratory (JPL) grant.

** A companion paper and press release is related to this research and should also be reviewed as part of any media interest. The press release, from Kansas University, is titled ‘Hot Neptune’ 260 light years away that ‘shouldn’t exist.’

Source: NASAS"s Spitzer Space Telescope/News

Monday, October 26, 2020

Green Light Unveils the Presence of an Old and Metal-Poor Halo in a Giant Elliptical Galaxy

Figure 1: (left) On-sky distribution of planetary nebulae observed with the Subaru Telescope (blue circles) and the PN.S at the William Herschel Telescope (red crosses). The background image from the Digitized Sky Survey shows the galaxies NGC 3384 (left) and M105 (center); (right) Suprime-Cam [OIII] (top-right) and V-band (bottom-right) cutouts of a small region in the halo of M105, with the detected planetary nebulae highlighted with blue circles. (Credit: J. Hartke (ESO)). Hi-res image

A team of astronomers using the Subaru Telescope has revealed a population of old and very metal-poor stars extensively surrounding the elliptical galaxy M105. The finding is important to further test the theory of formation of elliptical galaxies in galaxy groups, because these "free floating stars" are considered to be fossils proving that these groups form via extended processes through the continuous merging of smaller structures.

Galaxies are seldom found in isolation. Instead, most of them "live" in larger structures that are classified as groups or clusters, depending on their size and number of galaxies. How were these structures made? According to the standard cosmological model (Lambda-CDM model), these structures form hierarchically (bottom up), with smaller structures forming first and merging to form larger structures. Consequently, there must be a population of single stars unbound from the larger structures somewhere in the hierarchy. It then becomes important to find stars in the empty regions between galaxies that are in groups or clusters, and to determine through observations when the "free floating stars" began to appear and populate the surrounding space.

To identify a population of single stars scattered in a galaxy group, a team of astronomers, including members from the European Southern Observatory and the Max Plank Institute for Extraterrestrial Physics, studied the Leo I group at a distance of about 10 Mpc (33 million light-years), which is the closest group that contains all galaxy types (elliptical, spiral, and dwarf galaxies) with the elliptical galaxy M105 (NGC 3379) at its center.

The team used planetary nebulae (PNe) as tracers. PNe are the late stages of stars like our own Sun. In these stages, the central core becomes naked and the outer layers are expelled to form a nebula, that shines with a particular color, of aquamarine hue due to the oxygen [OIII] emission at 5007 Angstrom. A similar greenish color is also visible in the Earth's atmosphere as "northern lights." With the bright light from their envelopes, the dying stars are like beacons that astronomers can use to unveil the structure of the outermost regions of the galaxy M105.

The team used Suprime-Cam on the Subaru Telescope together with the Planetary Nebula Spectrograph (PN.S) mounted on the William Herschel Telescope, to carry out a complete census in the outer regions of M105. Figure 1 shows the distribution of PNe detected in the observed fields. Blue circles highlight the detections made with Suprime-Cam.

Once the census was completed, the team found an excess of PNe in the outer halo of M105, which significantly extends out to 50 kpc (160 kilo light-years), 18 times the effective radius (a "typical" size) of M105. In other words, there is an excess of old stars distributed in the outer halo. As in a detective story, the team then engaged in an investigation to look for the footprints of the parent stars of the detected PNe. By comparison with previous studies of red giant branch stars - the stellar ancestors of PNe - in the field, the team concluded that an old and very metal-poor population ([M/H] < -1.0) was "responsible" for generating the excess of PNe in the outer envelope encircling M105.

This was the breakthrough: This is the first study that has clearly established the link between the metal poor population and the excess of PNe in the outer regions of an elliptical galaxy. This outer component is faint – only 4% of the light in M105 reaches out to 18 effective radii, a region where it becomes possible to test the presence and the structure of dark matter. This will be investigated by measuring the velocities of the PNe and comparing the velocity dispersion profile with the dynamical models, e.g. for a single halo, or for a smaller halo within a larger halo of dark matter. Dr. Johanna Hartke, the lead author of the paper, comments on the future prospects, "This is especially interesting since M105 belongs to an elusive sample of galaxies, whose motions, as measured to date, are consistent with both very little dark matter as well as with massive dark matter halos. Our new, more extended data, will be able to firmly distinguish between these possibilities. "

This research was published in Astronomy and Astrophysics on October 7, 2020 (Johanna Hartke et al. "The halo of M105 and its group environment as traced by planetary nebula populations: I. Wide-field photometric survey of planetary nebulae in the Leo I group".)

See the link below for the details of this research.

Relevant Links

Green Light Unveils the Presence of an Old and Metal-Poor Halo in a Giant Elliptical Galaxy (Isaac Newton Group of Telescopes October 7, 2020 press release)

Source: Subaru Telescope

Friday, October 23, 2020

Einstein's Theory of Relativity, Critical for GPS, Seen in Distant Stars

The intriguing system known as 4U 1916-053 contains two stars in a remarkably close orbit. One is the core of a star that has had its outer layers stripped away, leaving a star that is much denser than the Sun. The other is a neutron star, an even denser object created when a massive star collapses in a supernova explosion. The neutron star (grey) is shown in this artist's impression at the center of a disk of hot gas pulled away from its companion (white star on left). Credit: Spectrum: NASA/CXC/University of Michigan/N. Trueba et al.; Illustration: NASA/CXC/M. Weiss

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What do Albert Einstein, the Global Positioning System (GPS), and a pair of stars 200,000 trillion miles from Earth have in common?

The answer is an effect from Einstein's General Theory of Relativity called the "gravitational redshift," where light is shifted to redder colors because of gravity. Using NASA's Chandra X-ray Observatory, astronomers have discovered the phenomenon in two stars orbiting each other in our galaxy about 29,000 light years (200,000 trillion miles) away from Earth. While these stars are very distant, gravitational redshifts have tangible impacts on modern life, as scientists and engineers must take them into account to enable accurate positions for GPS.

While scientists have found incontrovertible evidence of gravitational redshifts in our solar system, it has been challenging to observe them in more distant objects across space. The new Chandra results provide convincing evidence for gravitational redshift effects at play in a new cosmic setting.

These two compact stars are only about 215,000 miles apart, roughly the distance between the Earth and the Moon. While the Moon orbits our planet once a month, the dense companion star in 4U 1916-053 whips around the neutron star and completes a full orbit in only 50 minutes.

In the new work on 4U 1916-053, the team analyzed X-ray spectra — that is, the amounts of X-rays at different wavelengths — from Chandra. They found the characteristic signature of the absorption of X-ray light by iron and silicon in the spectra. In three separate observations with Chandra, the data show a sharp drop in the detected amount of X-rays close to the wavelengths where the iron or silicon atoms are expected to absorb the X-rays. One of the spectra showing absorption by iron – the dips on the left and right - is included in the main graphic. An additional graphic shows a spectrum with absorption by silicon. In both spectra the data are shown in grey and a computer model in red.

X-ray Spectra: Iron (Fe) & Silicon (Si)
Credit: NASA/CXC/University of Michigan/N. Trueba et al.

However, the wavelengths of these characteristic signatures of iron and silicon were shifted to longer, or redder wavelengths compared to the laboratory values found here on Earth (shown with the blue, vertical line for each absorption signature). The researchers found that the shift of the absorption features was the same in each of the three Chandra observations, and that it was too large to be explained by motion away from us. Instead they concluded it was caused by gravitational redshift.

How does this connect with General Relativity and GPS? As predicted by Einstein's theory, clocks under the force of gravity run at a slower rate than clocks viewed from a distant region experiencing weaker gravity. This means that clocks on Earth observed from orbiting satellites run at a slower rate. To have the high precision needed for GPS, this effect needs to be taken into account or there will be small differences in time that would add up quickly, calculating inaccurate positions.

All types of light, including X-rays, are also affected by gravity. An analogy is that of a person running up an escalator that is going down. As they do this, the person loses more energy than if the escalator was stationary or going up. The force of gravity has a similar effect on light, where a loss in energy gives a lower frequency. Because light in a vacuum always travels at the same speed, the loss of energy and lower frequency means that the light, including the signatures of iron and silicon, shift to longer wavelengths.

This is the first strong evidence for absorption signatures being shifted to longer wavelengths by gravity in a pair of stars that has either a neutron star or black hole. Strong evidence for gravitational redshifts in absorption has previously been observed from the surface of white dwarfs, with wavelength shifts typically only about 15% of that for 4U 1916-053.

Scientists say it is likely that a gaseous atmosphere blanketing the disk near the neutron star (shown in blue) absorbed the X-rays, producing these results. (This atmosphere is unrelated to the bulge of red gas in the outer part of the disk that blocks light from the inner part of the disk once per orbit.) The size of the shift in the spectra allowed the team to calculate how far this atmosphere is away from the neutron star, using General Relativity and assuming a standard mass for the neutron star. They found that the atmosphere is located 1,500 miles from the neutron star, about half the distance from Los Angeles to New York and equivalent to only 0.7% of the distance from the neutron star to the companion. It likely extends over several hundred miles from the neutron star.

In two of the three spectra there is also evidence for absorption signatures that have been shifted to even redder wavelengths, corresponding to a distance of only 0.04% of the distance from the neutron star to the companion. However, these signatures are detected with less confidence than the ones further away from the neutron star.

Scientists have been awarded further Chandra observation time in the upcoming year to study this system in more detail.

A paper describing these results was published in the August 10th, 2020 issue of The Astrophysical Journal Letter and also appears online. The authors of the paper are Nicolas Trueba and Jon Miller (University of Michigan in Ann Arbor), Andrew Fabian (University of Cambridge, UK), J. Kaastra (Netherlands Institute for Space Research), T. Kallman (NASA Goddard Space Flight Center in Greenbelt, Maryland), A. Lohfink (Montana State University), D. Proga (University of Nevada, Las Vegas), John Raymond (Center for Astrophysics | Harvard & Smithsonian), Christopher Reynolds (University of Cambridge), and M. Reynolds and A. Zoghbi (University of Michigan).

NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's CXC controls science and flight operations from Cambridge and Burlington, Massachusetts.

A Quick Look: Einstein's Theory of Relativity, Critical for GPS, Seen in Distant Stars

Source: NASA’s Chandra X-ray Observatory

Fast Facts for 4U 1916-53:

Category: Neutron Stars/X-ray Binaries
Coordinates (J2000): RA 19h 18m 47.87s | Dec -05° 14´ 17.1"
Constellation: Aquila
Observation Date: 1 Observation on Aug 7, 2004 and 10 observations between June 11-Aug 6, 2018
Observation Time: 80 hours 25 minutes (3 days 8 hours 25 minutes)
Obs. ID: 4584, 20171-20172, 21103-21106, 21662-21664, 21666
Instrument: ACIS
References: Trueba, N., et al., 2020, ApJL, v899, L16; arXiv:2008.01083
Distance Estimate: About 29,000 light years

Thursday, October 22, 2020

ALMA Shows Volcanic Impact on Io’s Atmosphere

This video shows images of Jupiter's moon Io in radio (made with ALMA), and optical light (made with Voyager 1 and Galileo missions). The ALMA images were taken when Io passed into Jupiter's shadow in March 2018 (eclipse), and from Jupiter's shadow into sunlight in September 2018. These radio images for the first time show plumes of sulfur dioxide (in yellow) rise up from the volcanoes on Io.Credit: ALMA (ESO/NAOJ/NRAO), I. de Pater et al.; NRAO/AUI NSF, S. Dagnello; NASA. Download Video

Composite image showing Jupiter's moon Io in radio (ALMA), and optical light (Voyager 1 and Galileo). The ALMA images of Io show for the first time plumes of sulfur dioxide (in yellow) rise up from its volcanoes. Jupiter is visible in the background (Cassini image).Credit: ALMA (ESO/NAOJ/NRAO), I. de Pater et al.; NRAO/AUI NSF, S. Dagnello; NASA/JPL/Space Science Institute. Hi-Res File

New radio images from the Atacama Large Millimeter/submillimeter Array (ALMA)vf Jupiter’s moon Io.

Io is the most volcanically active moon in our solar system. It hosts more than 400 active volcanoes, spewing out sulfur gases that give Io its yellow-white-orange-red colors when they freeze out on its surface.

Although it is extremely thin – about a billion times thinner than Earth’s atmosphere – Io has an atmosphere that can teach us about Io’s volcanic activity and provide us a window into the exotic moon’s interior and what is happening below its colorful crust.

Previous research has shown that Io’s atmosphere is dominated by sulfur dioxide gas, ultimately sourced from volcanic activity. “However, it is not known which process drives the dynamics in Io’s atmosphere,” said Imke de Pater of the University of California, Berkeley. “Is it volcanic activity, or gas that has sublimated (transitioned from solid to gaseous state) from the icy surface when Io is in sunlight?“

To distinguish between the different processes that give rise to Io’s atmosphere, a team of astronomers used ALMA to make snapshots of the moon when it passed in and out of Jupiter’s shadow (they call this an “eclipse”).

“When Io passes into Jupiter’s shadow, and is out of direct sunlight, it is too cold for sulfur dioxide gas, and it condenses onto Io’s surface. During that time we can only see volcanically-sourced sulfur dioxide. We can therefore see exactly how much of the atmosphere is impacted by volcanic activity,” explained Statia Luszcz-Cook from Columbia University, New York.

Thanks to ALMA’s exquisite resolution and sensitivity, the astronomers could, for the first time, clearly see the plumes of sulfur dioxide (SO2) and sulfur monoxide (SO) rise up from the volcanoes. Based on the snapshots, they calculated that active volcanoes directly produce 30-50 percent of Io’s atmosphere.

The ALMA images also showed a third gas coming out of volcanoes: potassium chloride (KCl). “We see KCl in volcanic regions where we do not see SO2 or SO,” said Luszcz-Cook. “This is strong evidence that the magma reservoirs are different under different volcanoes.”

Io is volcanically active due to a process called tidal heating. Io orbits Jupiter in an orbit that is not quite circular and, like our Moon always faces the same side of Earth, so does the same side of Io always face Jupiter. The gravitational pull of Jupiter’s other moons Europa and Ganymede causes tremendous amounts of internal friction and heat, giving rise to volcanoes such as Loki Patera, which spans more than 200 kilometers (124 miles) across. “By studying Io’s atmosphere and volcanic activity we learn more about not only the volcanoes themselves, but also the tidal heating process and Io’s interior,” added Luszcz-Cook.

A big unknown remains the temperature in Io’s lower atmosphere. In future research, the astronomers hope to measure this with ALMA. “To measure the temperature of Io’s atmosphere, we need to obtain a higher resolution in our observations, which requires that we observe the moon for a longer period of time. We can only do this when Io is in sunlight since it does not spend much time in eclipse,” said de Pater. “During such an observation, Io will rotate by tens of degrees. We will need to apply software that helps us make un-smeared images. We have done this previously with radio images of Jupiter made with ALMA and the Very Large Array (VLA).”

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Source: National Radio Astronomy Observatory (NRAO)/News

Media contact:

Iris Nijman
NRAO News and Public Information Manager
inijman@nrao.edu

Imke de Pater and Statia Luszcz-Cook worked with Patricio Rojo of the Universidad de Chile, Erin Redwing of the University of California, Berkeley, Katherine de Kleer of the California Institute of Technology (Caltech), and Arielle Moullet of SOFIA/USRA in California.

This research titled “ALMA Observations of Io Going into and Coming out of Eclipse” has been accepted for publication in The Planetary Science Journal. Preprint: https://arxiv.org/abs/2009.07729

Astronomy Cmarchesin

Saturday, October 31, 2020

Hubble Finds ‘Greater Pumpkin’ Galaxy Pair

Stars and Skulls: new ESO image reveals eerie nebula

Friday, October 30, 2020

A Quick Look: Assessing The Habitability of Planets Around Old Red Dwarfs

Assessing The Habitability of Planets Around Old Red Dwarfs

About Half of Sun-Like Stars Could Host Rocky, Potentially Habitable Planets

Thursday, October 29, 2020

NASA’s Webb To Examine Objects in the Graveyard of the Solar System

Wednesday, October 28, 2020

Galaxies in the Infant Universe Were Surprisingly Mature

Tuesday, October 27, 2020

Data reveals evidence of molecular absorption in the atmosphere of a hot Neptune

Monday, October 26, 2020

Green Light Unveils the Presence of an Old and Metal-Poor Halo in a Giant Elliptical Galaxy

Friday, October 23, 2020

Einstein's Theory of Relativity, Critical for GPS, Seen in Distant Stars

Thursday, October 22, 2020

ALMA Shows Volcanic Impact on Io’s Atmosphere

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